Multi-Led/Multi-Chip Color Mixing Optics

ABSTRACT

In one aspect, the present invention provides an optic, which comprises a light pipe extending from a proximal end to a distal end about an optical axis, said light pipe being adapted to receive at its proximal end at least a portion of light emitted by a light source. The optic further comprises a central reflector optically coupled to said distal end of the light pipe for receiving at least a portion of the light transmitted through the light pipe and reflecting said received light, a peripheral reflector optically coupled to said central reflector for receiving at least a portion of said reflected light, and an output surface. The peripheral reflect is configured to redirect at least a portion of the light received from the central reflector to said output surface for exiting the optic.

RELATED APPLICATIONS

The present application is a continuation application of U.S. Pat. No.14/441,691, filed May 8, 2015, which is a U.S. National Stage ofPCT/US2013/069184, filed Nov. 8, 2013, which claims priority to61/724,130, filed Nov. 8, 2012, all of which are herein incorporated byreference in their entirety.

FIELD

The present teachings relate generally to optics, lenses and lightingsystems and methods, and particularly to such optics, lenses andlighting systems and methods for light mixing and/or color mixing.

INTRODUCTION

Lenses and lighting systems for light sources, such as light emittingdiodes, can be utilized in a wide variety of applications. Many lightingapplications call for the ability to mix light emitted from a singlelight source, e.g., to obtain a desired light intensity profile and/orreduce source imaging. Further, in some applications, it is desirable tomix light emitted from multiple sources, e.g., sources producing lightof different wavelengths (i.e., colors). It is, however, difficult toproduce uniformly mixed light. Many conventional light-mixing systemsprovide textured surfaces to spread the light from a light source. Theefficiency and capabilities of such systems are limited and theirillumination characteristics are typically sub-par.

Accordingly, there is a need for improved light-mixing optics, lensesand respective lighting systems and methods.

SUMMARY

The present teachings generally disclose optics and optical systems inwhich a light pipe is employed for mixing light received from one ormore light sources and a combination of a central reflector (herein alsoreferred to in some cases as a fold mirror) and a peripheral reflectoris employed for redirecting and shaping the mixed light to form a beam(e.g., a collimated beam) for illuminating a target of interest. Whilein some embodiments, the reflective surfaces of central and theperipheral reflectors rely on total internal reflection for redirectingincident light, in other embodiments one or more of these reflectivesurfaces are formed by selective metallization of one or more surfacesof the optic. In some applications, the optics and the optical systemsof the invention can be used to mix light emitted by one or more arraysof multicolor light emitting diodes (LEDs) or LED chips to createuniform or nearly uniform light of any color (e.g., white) whileachieving narrow beam angles (e.g., FWHM at less than about 15 degrees).In some embodiments, the optics and the optical systems of the inventioncan be molded from a single piece of plastic, and can be readilytailored to fit a specific LED or LED array and/or mechanical constrainsof a specific lighting application. The optics and the optical systemsof the invention can provide a variety of output beams. For example, asdiscussed in more detail below, an output surface of an optic accordingto the present teachings can comprise a plurality of microlenses, whichallow tuning the shape of the output beam.

In one aspect, the present invention provides an optic, which comprisesa light pipe extending from a proximal end to a distal end about anoptical axis, said light pipe being adapted to receive at its proximalend at least a portion of light emitted by a light source. The opticfurther comprises a central reflector optically coupled to said distalend of the light pipe for receiving at least a portion of the lighttransmitted through the light pipe and for reflecting said receivedlight. A peripheral reflector is optically coupled to said centralreflector for receiving at least a portion of said reflected light. Theoptic further comprises an output surface through which light exits theoptic. The peripheral reflector is configured to redirect at least aportion of the light received from the central reflector to said outputsurface for exiting the optic.

In some embodiments, the central reflector is configured to reflect atleast a portion of the light received from the light pipe via totalinternal reflection (TIR). In other embodiments, the central reflectoris configured to reflect at least a portion of the light received fromthe light pipe via specular reflection. Further, in some embodiments,the central reflector is configured to reflect the light received fromthe light pipe via a combination of TIR and specular reflection.

The lateral reflector can comprise a lateral surface, which isconfigured to receive at least a portion of the light reflected by thecentral reflector and to redirect the received light to the outputsurface for exiting the optic. In some embodiments, the lateral surfaceis configured to redirect the received light along a direction that issubstantially parallel to said optical axis. While in some embodimentsthe lateral surface is configured to reflect the light incident thereonvia TIR, in other embodiments the lateral surface is configured toreflect the incident light via specular reflection or a combination ofTIR and specular reflection.

In some embodiments, the lateral surface can further include anotherreflective surface that is disposed at an angle (typically an acuteangle) relative to said lateral surface.

This additional reflective surface is configured to receive anotherportion of light reflected by the central reflector and to redirect thereceived light via reflection, e.g., via TIR, specular reflection or acombination of TIR and specular reflection, to any of said lateralsurface and said output surface. In some embodiments, this additionalreflective surface is a substantially flat surface that is positionedsubstantially perpendicular to the optical axis.

The light redirected by this additional reflective surface to thelateral surface can be reflected by the lateral surface toward theoutput surface for exiting the optic. In some embodiments, the lightthat is reflected by this additional reflective surface directly towardthe output surface propagates in a direction substantially parallel tothe optical axis to the output surface.

The central reflector of the optic can comprise a reflective surfacethat reflects the light incident thereon via TIR, specular reflection orboth. In some embodiments, this reflective surface can be in the form ofan inverted conical surface whose apex is disposed on the optical axis.In some embodiments, this reflective surface can comprise a plurality ofsurface undulations (e.g., surface oscillations). The surfaceundulations can further mix the light received from the light pipe.

In some embodiments, the output surface of the optic comprises atextured surface to cause further mixing of the light rays as they exitthe optic. In some embodiments, the output surface of the opticcomprises a plurality of microlenses to cause further mixing of thelight rays as they exit the optic.

The optic can be employed to mix and redirect light emitted by aplurality of different light sources. Some examples of such lightsources comprise, without limitation, a single light emitting diode(LED), a plurality of discrete LEDs, one or more multi-LED chips, amongothers.

While in some embodiments the optic is formed as a single unitary piece,in other embodiments, the optic can be formed of separated pieces thatare assembled together to provide the above functionality.

In a related aspect, an optical system is disclosed, which comprises alight source, and an optic that is coupled to said light source forreceiving light therefrom and to redirect the received light, e.g., as acollimated beam. The optic can comprise a light pipe extending from aproximal end to a distal end about an optical axis, said light pipebeing adapted to receive at its proximal end at least a portion of lightemitted by a light source, a central reflector optically coupled to saiddistal end of the light pipe for receiving at least a portion of thelight transmitted through the light pipe and for reflecting saidreceived light, a peripheral reflector optically coupled to said centralreflector for receiving at least a portion of said reflected light, andan output surface. The peripheral reflector is configured to redirect atleast a portion of the light received from the central reflector to saidoutput surface for exiting the optic.

In a related aspect, an optic is disclosed, which comprises a light pipehaving an input surface for receiving light from a light source and anoutput surface through which light exits the light pipe. An opticalcomponent is optically coupled to said output surface of the light pipeto receive at least a portion of the light exiting the light pipe, saidoptical component comprising an input surface through which at least aportion of the light exiting the light pipe enters the opticalcomponent, a central reflector configured to receive at least a portionof the light entering the optical component and to reflect at least aportion of the received light, a peripheral reflector optically coupledto said central reflector for receiving at least a portion of saidreflected light, and an output surface. The peripheral reflector isconfigured to redirect at least a portion of the light received from thecentral reflector to said output surface.

The following detailed description in conjunction with the associateddrawings, which are described briefly below, further disclose variousaspects of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic cross-sectional view of an embodiment of an opticaccording to the teachings of the invention,

FIG. 1B is a schematic perspective view of the optic shown in FIG. 1A.

FIG. 1C is another schematic perspective view of the optic shown in FIG.1A.

FIG. 2 is a schematic cross-sectional view of an optic according to anembodiment of the invention, which includes a plurality of micro lenseson an output surface thereof,

FIG. 3 shows theoretically calculated paths of a plurality of light raysemitted by a source through an embodiment of an optic according to theteachings of the invention,

FIG. 4 is schematic cross-sectional view of an optic according to theteachings of the invention, which is coupled to two light sources formixing the light emitted thereby and shaping the mixed light as acollimated beam,

FIG. 5 is a top schematic perspective view of an optic according to anembodiment of the invention, which comprises a central undulatingreflective surface,

FIG. 6 is a schematic cross-sectional view of an optic according to anembodiment of the invention, which includes a plurality of separateoptical components assembled to provide cooperatively the optic'sfunctionality, and

FIG. 7 is a schematic cross-sectional view of an embodiment of the opticof FIG. 6 in which a plurality of surfaces comprise microlenses.

DETAILED DESCRIPTION

FIGS. 1A, 1B, and 1C schematically depict an optic 10 according to anembodiment of the invention, which includes a light pipe 12, a centralreflector 14 and a peripheral reflector 18. The light pipe 12 extendsbetween a proximal end (PE) to a distal end (DE) about an optical axis(OA). The light pipe 12 can have a variety of different cross-sectionalshapes. In many embodiments, the light pipe 12 has a polygonalcross-sectional shape (in a plane perpendicular to the optical axis(OA)), such as, square, rectangle, hexagonal, etc. In some embodiments,the cross-sectional area of the light pipe at its distal end can begreater than the cross-sectional area at its proximal end. In thisexemplary embodiment, the light pipe exhibits a progressively increasingcross-sectional area from its proximal end to its distal end. In otherembodiments, the cross-sectional area of the light pipe can be constantfrom its proximal end to its distal end. The light pipe is adapted toreceive at its proximal end, via an input surface 12 a, light from oneor more light sources 20 that are optically coupled thereto.

A variety of light sources, including incoherent and coherent lightsources, can be employed. By way of example, the light source 20 can bea single light emitting diode (LED), a plurality of discrete lightemitting diodes, a multi-LED chip, among others.

Many of the light rays entering the light pipe via its input surface 12a undergo multiple reflections at its lateral surfaces (i.e., surfaces12 b, 12 c, 12 d and 12 e) as they propagate along the light pipe towardits distal end. In this embodiment, the light pipe is configured, in amanner known in the art, so that the light rays incident on its lateralsurfaces undergo total internal reflection (TIR). For example, therefractive index of the material forming the light pipe and the shapesof the lateral surfaces of the light pipe are chosen such that many, andpreferably all, of the light rays incident on those surfaces, as theypropagate along the light pipe, would undergo TIR. In some embodiments,the lateral surfaces can be metalized to allow specular reflection ofthe incident light rays. Further, in some embodiments, the reflection ofthe light rays incident on the lateral surfaces of the light pipe can beachieved via a combination of specular and total internal reflection.

The multiple reflection of the light rays by lateral surfaces of thelight pipe causes the mixing of those rays. Such mixing of the lightrays can be advantageous in a variety of lighting applications. Forexample, in certain applications in which a single light source isemployed, such mixing of the light rays can improve intensityhomogeneity in a plane perpendicular to the direction of propagation. Incertain applications in which light sources of different colors areemployed, such mixing of the light rays can provide enhanced colormixing.

With continued reference to FIGS. 1A, 1B, and 1C, the central reflector14 is optically coupled to the distal end of the light pipe to receiveat least a portion of the light transmitted through the light pipe. Inthis embodiment, the central reflector 14 is in the form of an invertedconical reflective surface 14 a whose apex 14 b is disposed on theoptical axis (OA). In this embodiment the reflective surface 14 a isconfigured, in a manner known in the art, to reflect via TIR the lightrays incident thereon via transmission through the light pipe 12. Forexample, the refractive index of the material forming the optic as wellas the shape and configuration of the reflective surface 14 b, e.g., theopening angle a, can be selected such that the incident light rays, orat least a substantial portion thereof (e.g., at least about 80% or90%), would reflect via TIR by the reflective surface 14 a.Alternatively, or in addition, the reflective surface 14 a can include ametallic coating to effect specular reflection of the incident lightrays.

In this embodiment, the reflective surface 14 a redirects the incidentlight rays to the peripheral reflector 18, which includes a peripheralreflective surface 18 a that is configured to receive a portion of thelight reflected by the reflective surface 14 a and another reflectivesurface 18 b positioned at an angle relative to the peripheralreflective surface 18 a, which is configured to receive another portionof the light reflected by the reflective surface 14 a. In thisembodiment, the reflective surface 18 b is a substantially flat surfacethat is positioned perpendicularly relative to the optical axis (OA).The reflective surfaces 18 a and 18 b redirect the incident light rays,via reflection, to an output surface 22 through which the light raysexit the optic. (The reflective surface 14 a is also herein referred toin some cases as a fold mirror as a way of indicating that it redirectsthe light rays leaving the light pipe away from their propagationdirection as they exit the light pipe).

In various embodiments, the optic 12 can be configured such that asubstantial portion of light exiting the output surface 22 exhibits anarrow beam angle. For example, the surfaces 18 a and 18 b can beconfigured to redirect a substantial portion of the incident light raystowards the output surfaces 22 in a direction that is substantiallyparallel to the optical axis. In this manner, the peripheral reflector18 can collimate the light received from the central reflector 14 forexiting the optic through the output surface 22. In some embodiments,for example, the optic 12 can be configured such that the light exitingeach output surface 22 can exhibit FWHM at less than about 15 degrees,less than about 10 degrees, or less than about 5 degrees.

In this embodiment, the reflective surfaces 18 a and 18 b are configuredto reflect the incident light, or at least a substantial portion thereof(e.g., more than about 80%, or 90%), via TIR. Alternatively or inaddition, a thin metal coating (not shown) can cover at least a portionof the surfaces 18 a and 18 b to effect specular reflection of the lightrays at those surfaces.

In this embodiment, the output surface 22 is substantially flat. Inother embodiments, the output surface can be textured and/or include aplurality of microlenses, e.g., to cause additional mixing of the lightrays as they exit the optic therethrough. By way of example, FIG. 2schematically depicts such an embodiment in which the output surface 22comprises a plurality of microlenses 24. In color mixing applications,the microlenses can improve color mixing. Further, the microlenses canbe employed to achieve greater output beam angles or create anelliptical output beam.

Referring to FIG. 3, in use, the optic 10 can receive light at itsproximal end from the light source 20. The received light is transmittedthrough the light pipe 12 and is reflected by the central reflector 14to the peripheral reflector 18, which in turn redirects the light as acollimated set of rays toward the output surface 22 for exiting theoptic. In this manner, the light pipe 12 homogenizes the light output ofthe source 20, e.g., an LED array, while the central reflector 14 andthe peripheral collimating reflector 18 form the beam shape. Asdiscussed otherwise herein, the central reflector 14 and peripheralreflector 18 can be configured such that the light exiting each outputsurface 22 can exhibit FWHM at less than about 15 degrees, less thanabout 10 degrees, or less than about 5 degrees.

The optic 10 can be made in a variety of different sizes, shapes andaspect ratios, e.g., based on a particular lighting application forwhich the optic is intended. For example, the sizes of the input and theoutput surfaces 12 a and 22, the length of the light pipe, the lengthsand the diameters of the central and the peripheral reflectors as wellas the profiles of their reflective surfaces can be adjusted, e.g.,based on an application for which the optic is intended. By way ofexample, the ratio of the length (L) of the light pipe relative to thediameter (D_(input)) of the its input surface can be in a range of about3:1 to about 1:1. The ratio of the diameter (D_(output)) of the outputsurface 22 of the optic relative to D_(input) can be selected, e.g., atleast partially based on the desired level of collimation of the lightrays exiting the optic. For example, in some embodiments in -which acollimation characterized by a divergence of less than about 10 degreesis desired, the ratio of D_(output) relative to D_(input) can be in arange of about 10:1 to about 20:1.

In this embodiment, the optic 10 is fabricated as a single integralunit. A variety of materials and manufacturing techniques can beemployed to form the optic 10. Some examples of suitable materialsinclude, without limitation, PMMA, polycarbonate, glass, silicon, andany optically clear material. Some examples of suitable manufacturingtechniques include, without limitation, injection molding. While in manyembodiments different parts of the optic are formed of the samematerial, in other embodiments different materials may be used to formdifferent parts of the optic. For example, one material can be employedto form the light pipe while another material is used to form theremainder of the optic.

FIG. 4 schematically depicts that the optic 10 can be employed withmultiple light sources (in this embodiments two light sources 24 a and24 b) to mix the light emitted by those sources and direct the mixedlight as a substantially collimated beam out of the optic. In thisembodiment, the light sources 24 a and 24 b generate light of differentcolors. The passage of the light rays emitted by the sources 24 a and 24b through the light pipe 12 causes their mixing (in this illustration,the light rays associated with one source are shown by solid lines whilethe light rays associated with the other source are shown by brokenlines). The central and the peripheral reflectors, in turn, redirect themixed light transmitted through the light pipe out of the optic, via theoutput surface 22, as a substantially collimated beam. In this manner,the optic 10 can be utilized for color mixing applications, amongothers.

In some embodiments, the central reflector of the optic 10 discussedabove can have an undulating reflective surface. For example, as shownschematically in FIG. 5, such an optic 10′ can include a centraloscillating reflective surface 12′a (the remainder of the optic in thisexample is identical to the optic 10 discussed above). The oscillationsof the reflective surface 12′ can cause further mixing of the light raysreflected thereby. By way of example, such additional mixing of thelight rays can improve color mixing in lighting applications.

While in some embodiments the optic is formed as a single unitary piece(such as the optic 10 discussed above), in other embodiments the opticcan be formed of separated pieces (separate optical components) that canbe assembled relative to one another so as to cooperatively provide theoptic's functionality. By way of example, FIG. 6 schematically depictsan optic 100 (herein also referred to as an optical system) thatincludes two optical components 102 and 104 that are optically coupledto one another. The optical component 102 is a light pipe that extendsabout an optical axis (OA) from a proximal end (PE) to a distal end(DE). The light pipe is configured to receive light from one or morelight sources at its input surface 102 a and to transmit the receivedlight to its output surface 102 b. Similar to the previous embodiments,the light pipe 102 exhibits a progressively increasing cross-sectionalarea from its input surface to its output surface (in anotherembodiment, the light pipe can have a substantially constantcross-sectional area). The optical component 104 receives, via a centralportion 106 a of its surface 106, the light exiting the light pipe (atleast a portion of this light). A central reflective surface 108, whichis in the form of an inverted conical surface, directs a portion of thelight incident thereon, via reflection, to a lateral reflective surface110, and another portion of the incident light to a peripheral portion106 b of the surface 106. The lateral reflective surface 110 reflectsthe light incident thereon, via TIR, specular reflection or acombination of the two, to an output surface 112 for exiting the optic.In some embodiments, a portion of the light reflected by the peripheralportion 106 b (e.g., via TIR, specular reflection or both) reaches theoutput surface 112 directly and another portion of such reflected lightreaches the output surface 112 via reflection at the lateral reflectivesurface 110.

In some embodiments of the above optic 100, the output surface 102(b) ofthe light pipe can comprise a textured surface and/or a plurality ofmicro lenses. Alternatively or in addition, the central portion 106 a ofthe surface 106 of the optical element 104 and/or the output surface 112thereof can comprise a textured surface and/or a plurality ofmicrolenses. As noted above, this can improve mixing of the light rays.The improvement in light mixing can be advantageous in a variety ofapplications, such as color mixing. By way of example, FIG. 7schematically depicts an optic 100′ according to such an embodiment inwhich an output surface 102′b of the light pipe, a central portion 106′aof the optical element 104′ and an output surface 112′ of the opticcomprise, respectively, a plurality of microlenses 114, 116, 118.

Those having ordinary skill in the art will appreciate that a variety ofmodifications can be made to the above embodiments without departingfrom the scope of the invention.

1.-15 (canceled)
 16. An optic, comprising a light pipe extending from aproximal end to a distal end about an optical axis, said light pipebeing adapted to receive at its proximal end at least a portion of lightemitted by a light source, and a reflector optically coupled to thedistal end of the light pipe to receive at least a portion of lightexiting the light pipe and redirecting said received light via one ormore reflections.